Pulse generating circuit



June 5, 1956 M. KATZIN 2,749,452

PULSE GENERATING CIRCUIT Filed Aug. 25, 1950 NETWORK NETWORK O C O O TO MAGNETRON CATHODE INVENTOR MARTIN KATZIN BY 7LqM M ATTORNEYS United rates Fatent O PULSE GENERATING CIRCUIT Martin Katzin, Washington, D. C.

Application August 25, 1950, Serial No. 181,536

4 Claims. (Cl. 307-106) (Granted under Title 35, U. S. Code (1952), sec. 266) This invention relates to voltage pulse generating circuits. More particularly it relates to a pulse generating circuit for generating in any desired sequence pulses of high voltage direct current having different time durations.

Circuits for generating high voltage direct current pulses of a uniform time duration and a recurrence frequency of the order of one thousand cycles per second are well known in the art of radio echo ranging devices. Such pulses may be used, for example, to produce the short duration, high voltage energy necessary to operate the high power radio frequency oscillator, such as a magnetron tube, common to the transmitters of such radio echo ranging devices.

Often in radio echo ranging systems it may be desirable to obtain the advantages inherent in operation with a transmitted pulse signal of very short time duration, or width, and at the same time to combine therewith the advantages obtainable from operation with a transmitted pulse signal of greater time duration, or width. With such a system the variable pulse Width pulse generating circuit described herein may have particular utility.

It is an object of this invention, therefore, to provide a voltage pulse generating circuit for generating recurrent voltage pulses of variable time duration.

Another object of this invention is to provide a pulse generating circuit for generating voltage pulses of variable duration in a desired sequence.

Another object is to provide a relatively simple and flexible circuit for generating pulses having an alternative time duration for use with the transmitter of a radio echo ranging system.

Other, objects and features of the present invention will appear more fully hereinafter from the following detailed description considered in connection with the accompanying drawings which disclose one embodiment of the invention. It is expressly understood, however, that the drawings are designed for purposes of illustration only and not as a definition of the limits of the invention, reference for the latter purpose being had to the appended claims.

In the drawings, wherein like reference characters refer to like elements in all the figures:

Fig. 1 shows an elementary schematic diagram of a circuit constructed in accordance with the present invention,

Fig. 2 shows a more detailed schematic diagram of the circuit of Fig. l, with certain additional refinements.

Briefly this invention provides for modifying a conventional pulse generating circuit to include additional pulse forming potential storage means, and switching hte additional potential storage means into the conventional circuit in a desired sequence, to form upon discharge voltage pulses of varying lengths.

As shown in Fig. 1, a pulse generating circuit constructed in accordance with this invention may include a source of direct current voltage 1 connected in series with a load impedance 2 through a charging path including inductance 3, an isolating diode 4, and a pulse forming potential storage network 5. The network 5 may be an artificial 2,749,452 Patented June 5, 1956 transmission line of conventional design, consisting of a number of lumped inductances and capacitances and having a characteristic impedance Ze. This characteristic impedance Z0 is chosen to match the load impedance 2. One side of voltage source 1 and one side of load impedance 2 is connected to ground.

The potential storage network 5 is also provided with a discharge path 6 including a switch 7, one side of which is grounded. Load impedance 2 is common to both the charging and discharging paths.

The circuit thus far described is conventional in the voltage pulse generating art. Its operation is as follows: Considering the sequence of events immediately following the commencement of current flow through diode 4, the components of network 5 are charged by the current flowing from voltage source 1 through the series charging path including inductance 3, diode 4, and load impedance 2. Because of the presence of inductance 3, the value of which is chosen to produce the phenomenon well known in the art as resonant charging, network 5 stores a charge whose potential is twice the source voltage 1.

If upon completion of the charging cycle, when the current inductance 3 becomes zero, switch 7 is closed, network 5 will be abruptly discharged through the series path including switch 7 and load impedance 2. The discharge current thus produced will create a voltage across load impedance 2 equal to one-half the storage potential of network 5, i. e., equal to the source voltage 1. This voltage will appear across load impedance 2 as a pulse having a relatively constant amplitude and short duration. This pulse duration is determined by the values of the components chosen for network 5 in accordance with well known design considerations. Upon the termination of the discharge current from network 5, the voltage across load impedance 2 will drop abruptly to zero.

The circuit operation thus far described is conventional and well known in the pulse generating art. It is included in brief here only to assist in particularly pointing out the novelty of applicants invention, which will be described as follows:

When it is desired to develop a voltage pulse across load impedance 2 having an alternative and greater time duration than the pulse developed during the discharge of network 5, alone, an additional network 10, having the same characteristic impedance as network 5, may be connected into the circuit electrically in parallel with network 5. By such a connection the duration of the pulse discharge from the two networks is made the sum of those from the two networks individually. The high voltage terminals of networks 5 and 10 may be connected directly, and the low voltage terminals may be connected through a unidirectional switch 11. Switch 11 is made unidirectional to permit charging current from voltage source 1 to charge both networks 5 and 10 simultaneously, through the series charging path including inductance 3, diode 4 and load impedance 2. The value of inductance 3 is adjusted to provide resonant charging of the total number of energy storage components composing networks 5 and 10.

Connected in parallel with switch 11 is an additional switch 12, made unidirectional to pass current flowing in the opposite direction to that which will be passed by switch 11.

If new the circuit is operated with switch 11 closed and switch 12 open, both network 5 and network 10 will charge up during the charging cycle. When switch 7 is closed, however, only network 5 is provided with a completely closed discharge path through load impedance 2. This forms a voltage pulse at 2 having the same duration as if network 10 were not present. After the first charging cycle, network 10 retains a fixed charge independent of the charging and discharging of network 5.

However, when switch 12 is also closed, a complete discharge path is provided for both network and network 10. Closing of switch 7 then produces a voltage pulse across load impedance 2 having :the same amplitude as before, but a time duration, or Width, increased 'by an amount determined by the values of the components chosen for network 10.

It will be'readi-ly apparent from the above description that-either a short or long duration pulse may be developed across load impedance 2 each time switch 7 is closed, depending on whether switch 12 is open or closed.

Turning now :to Fig. 2, there is shown a'circuit including details of refinement which provide an "increase in utility over the elementary circuit of Fig. 1.

Load impedance 2 is depicted as the primary winding of a magnetron cathode pulse transformer. Switch '7 is shown as a grid-controlled thyratron, normally biased 'to'be non-conducting by grid resistor 20 and bias battery 24. 'Thyratron 7 is adapted to be fired by a trigger pulse synchronized with the end of the charging cycle, and emanating from synchronizer 21. Switch 11 has been replaced by a diode, .50 connected as to pass the charging current flowing from network 10 to load impedance 2. Switch 12 has been replaced by a grid-controlled thyratron, normally non-conducting, and adapted to be fired by control pulses fed to transformer 22.

The control pulses for rendering thyratron 12 conducting, and enabling network 10 to be discharged simultaneously with network 5, may be derived for example from a frequency divider 23 fed by the pulses from 'synchronizer 21. Each output pulse from frequency divider 23 must be isochronous with a pulse from synchronizer 21. For example, the frequency divider output pulses may be made isochronous with any desired submultiple of the synchronizing trigger pulses fed to switch 7. Pulses for firing thyratron 12, however, need not be confined to those which bear simple relationships,

such as submultiples, to the synchronizer pulses. The firing pulses for thyratron 12 may be produced in any desired or predetermined sequence relative to the pulses from synchronizer 21, for example with a cam arrangement, pulse counting circuit or similar device well known to the prior art, so long as each pulse produced will fire thyratron '12 at the same instant thyratron 7 ,isfired. Thus both networks may be discharged, and the longer duration voltage pulse may be obtained across load impedance 2, in any desired sequence relative to the short duration pulses derived from the discharge of network Salone.

Although only one embodiment of the'present invention has been disclosed and described herein, it is 'expressly understood that various changes and substitutions may be made therein without departing from the spirit of the invention as well understood by those skilled in the art. For example, it will be apparent that jswitches 7, 11 and 12 may assume any of their respective equivalent forms. Also switches 11 and 12 may connect the high voltage, rather than the low voltage, terminals of'networks 5 and 10. Additional synchronized switches may be provided to discharge any one network and/ or an additional network or networks in any desired sequence. Also an additional switch synchronized with the operation of switch 12 may be provided to substitute an alternative load in place of load impedance 2 for use with the longer duration pulses. Reference therefore will be had to the appended claims for a definition of the limits of the invention.

The invention described herein may be manufactured and used by or for the Government of 'theUnited States of America for governmental purposes without the payment of any royalties thereon-or therefor.

What'is claimed is:

"1. Means for generating alternative width voltagerpulses in a particular sequence comprising a first and a second potential storage device, means for simultaneously charging said potential storage devices at a first recurrence rate, a load impedance connected in series with said first potential storage device, means generating a series of first trigger pulses, means operative responsive to said first trigger pulses for discharging the first potential storage device through said load impedance to form voltage pulses having a first duration, means for generating second trigger pulses coincident with predetermined pulses in said series of first trigger pulses, and means operative responsive to said second trigger pulses for connecting said second potential storage device in parallel with said first storage device for discharging said second potential storage-device simultaneously with said first potential storage device to form voltage pulses having a second duration.

2. in a voltage pulse generating circuit including .a first potential storage device, a potential source, and a discharge path for said first potential storage device including .a load impedance; means generating a series of first trigger pulses; a first electron discharge device operative responsive to said first trigger pulses for discharging said first potential storage device through said discharge path at a first recurrence rate to form first voltage pulses having a first duration; means charging said first potential storage device from said potential source intermittent the operation of said first electron discharge device; a second potential storage device; means for charging said second potential storage device simultaneously with said first potential storage device; and a second electron discharge device operative responsive to a predetermined one of said first trigger pulses for connecting said second potential storage device in parallel with said first potential storage device for discharging said second potential storage device With said first potential storage device to-form a second voltage pulse having a second duration.

3. A voltage pulse generating circuit for generating variable time duration pulses across a load impedance comprising a plurality of energy storage devices, means including an electrical energy source for simultaneously chargingsaid storage devices, a load impedance connected in series with a first of said energy storage devices, means for recurrently discharging the first of said storage devices through the said load impedance to produce voltage pulses of a first duration, means periodically connecting additional storage devices in parallel with the first mentioned storage device whereby said discharging means will discharge a plurality of storage devices simultaneously through the load impedance to produce voltage pulseshaving durations different from the first mentioned duration.

4. A voltage pulse generating circuit for generating variable time duration pulses across a load impedance comprising a plurality of artificial transmission lines, means for charging said plurality of artificial transmission lines, means for recurrently discharging a first of said References Cited in the file of this patent UNITED STATES PATENTS 2,420,309 Goodall May 13,1947 2,496,979 Blumlein Feb. 7., 1950 2,606,289 Stanton AugJS, 1952 

